In a conventional motor control apparatus, motor control is changed based on a fail-safe concept when an occurrence of failure is detected. The failure may be a failure in an inverter, a power relay or the like, which form a part of the motor control apparatus. The failure may also be a failure in a current sensor, a rotation angle sensor or the like, which detects each physical quantity inputted to the motor control apparatus. The motor control apparatus is caused to fail by not only a failure in a hardware part but also bugs in control software, which a microcomputer executes.
According to the apparatus disclosed in JP 4496205 (US 2008/0147949 A1), a check device in hardware configuration is provided separately from a microcomputer so that the check device executes the same calculation as that of the microcomputer or simplified calculation independently of the microcomputer. The calculation results of the microcomputer and the check device are compared to detect a software abnormality of the microcomputer.
The apparatus needs the check device (hardware device) separately from the microcomputer. The microcomputer outputs signals to the hardware device through a communication line. If the number of output signals increases depending on combinations of parameters to be monitored, a range of monitoring need be limited to avoid erroneous detections.
Further, a speed of communication by the communication line is also limited.